Alternative migratory tactics in brown trout (Salmo trutta) are underpinned by divergent regulation of metabolic but not neurological genes

Paralog switching facilitates diadromy: ontogenetic, microevolutionary and macroevolutionary evidence

Identifying how the demands of migration are met at the level of gene expression is critical for understanding migratory physiology and can potentially reveal how migratory forms evolve from nonmigratory forms and vice versa. Among fishes, migration between freshwater and seawater (diadromy) requires considerable osmoregulatory adjustments, powered by the ion pump Na+, K+-ATPase (NKA) in the gills. Paralogs of the catalytic α-subunit of the pump (NKA α1a and α1b) are reciprocally upregulated in fresh- and seawater, a response known as paralog-switching, in gills of some diadromous species. We tested ontogenetic changes in NKA α-subunit paralog expression patterns, comparing pre-migrant and migrant alewife (Alosa pseudoharengus) sampled in their natal freshwater environment and after 24 h in seawater. In comparison to pre-migrants, juvenile out-migrants exhibited stronger paralog switching via greater downregulation of NKA α1a in seawater. We also tested microevolutionary changes in the response, exposing juvenile diadromous and landlocked alewife to freshwater (0 ppt) and seawater (30 ppt) for 2, 5, and 15 days. Diadromous and landlocked alewife exhibited salinity-dependent paralog switching, but levels of NKA α1b transcription were higher and the decrease in NKA α1a was greater after seawater exposure in diadromous alewife. Finally, we placed alewife α-subunit NKA paralogs in a macroevolutionary context. Molecular phylogenies show alewife paralogs originated independently of paralogs in salmonids and other teleosts. This study demonstrated that NKA paralog switching is tied to halohabitat profile and that duplications of the NKA gene provided the substrate for multiple, independent molecular solutions that support a diadromous life history.

Differentiation and Maturation of Muscle and Fat Cells in Cultivated Seafood: Lessons from Developmental Biology

Cultivated meat, also known as cultured or cell-based meat, is meat produced directly from cultured animal cells rather than from a whole animal. Cultivated meat and seafood have been proposed as a means of mitigating the substantial harms associated with current production methods, including damage to the environment, antibiotic resistance, food security challenges, poor animal welfare, and-in the case of seafood-overfishing and ecological damage associated with fishing and aquaculture. Because biomedical tissue engineering research, from which cultivated meat draws a great deal of inspiration, has thus far been conducted almost exclusively in mammals, cultivated seafood suffers from a lack of established protocols for producing complex tissues in vitro. At the same time, fish such as the zebrafish Danio rerio have been widely used as model organisms in developmental biology. Therefore, many of the mechanisms and signaling pathways involved in the formation of muscle, fat, and other relevant tissue are relatively well understood for this species. The same processes are understood to a lesser degree in aquatic invertebrates. This review discusses the differentiation and maturation of meat-relevant cell types in aquatic species and makes recommendations for future research aimed at recapitulating these processes to produce cultivated fish and shellfish.

Non-Lethal Sampling Supports Integrative Movement Research in Freshwater Fish

Freshwater ecosystems and fishes are enormous resources for human uses and biodiversity worldwide. However, anthropogenic climate change and factors such as dams and environmental contaminants threaten these freshwater systems. One way that researchers can address conservation issues in freshwater fishes is via integrative non-lethal movement research. We review different methods for studying movement, such as with acoustic telemetry. Methods for connecting movement and physiology are then reviewed, by using non-lethal tissue biopsies to assay environmental contaminants, isotope composition, protein metabolism, and gene expression. Methods for connecting movement and genetics are reviewed as well, such as by using population genetics or quantitative genetics and genome-wide association studies. We present further considerations for collecting molecular data, the ethical foundations of non-lethal sampling, integrative approaches to research, and management decisions. Ultimately, we argue that non-lethal sampling is effective for conducting integrative, movement-oriented research in freshwater fishes. This research has the potential for addressing critical issues in freshwater systems in the future.